Known gas turbine engines generally include rows of circumferentially spaced nozzles and buckets. A turbine bucket generally includes an airfoil having a pressure side and a suction side and extending radially upward from a platform. A hollow shank portion may extend radially downward from the platform and may include a dovetail and the like so as to secure the turbine bucket to a turbine wheel. The platform generally defines an inner boundary for the hot combustion gases flowing through a gas path. As such, the platform may be an area of high stress concentration due to the hot combustion gases and the mechanical loading thereon.
More specifically, there is often a large amount of thermally induced strain at the intersection of an airfoil and a platform. This thermally induced strain may be due to the temperature differential between the airfoil and the platform. The thermally induced strain may combine with geometric discontinuities in the region so as to create areas of very high stress that may limit component lifetime. To date, these issues have been addressed by attempting to keep geometric discontinuities such as root turns, internal ribs, and the like, away from the intersection. Further, attempts have been made to control the temperature about the intersection. Temperature control, however, generally requires additional cooling flows at the expense of overall engine efficiency. These known cooling arrangements, however, thus may be difficult and expensive to manufacture and may require the use of an excessive amount of air or other types of cooling flows.
There is thus a desire for an improved turbine bucket for use with a gas turbine engine. Preferably such a turbine bucket may limit the stresses at the intersection of an airfoil and a platform without excessive manufacturing and operating costs and without excessive cooling medium losses for efficient operation and an extended component lifetime.